<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>
<script>
    var A = function () {

    }
    A.prototype.n = 1
    var b = new A();// b.__proto__ === x010101  ----->{n:1}
    A.prototype = {// A.prototype 的引用地址发生改变
        n: 2,
        m: 3
    }
    var c = new A();// c.__proto__ === x00900======>{n:2,m:3}
    // console.log(b.__proto__ === c.__proto__);
    console.log(b.n, b.m, c.n, c.m);// 1 undefined 2 3
</script>
</html>